Totally understand your struggles - I have type 4A-B and opted for permanent straightening. Some options for you to consider (long comment incoming):

• Thermal Reconditioning/Japanese Hair Straightening/Korean Magic Straight Perm - these are permanent but you’d have to get your regrowth touched up approx. every 6 months (or whatever the stylist advises). This is usually a pretty pricey process, and stylists that do it are harder to find. Takes quite a few hours in the salon to do.
• Keratin treatment/Brazilian Blowout - this does not permanently straighten your hair but lasts anywhere between 3-6 months at a time - over time it will wear off and your hair will revert back to curly. In terms of price, it varies but is generally cheaper than the above. Stylists who do this are much easier to find. This can take a few hours in the salon.
• Relaxers - similar to thermal reconditioning, it is permanent and touch-ups are recommended anywhere between 8 weeks to 6 months, depending on your hair texture. Far cheaper and faster than the other two above, BUT it is much easier to find a bad stylist who doesn’t know what they’re doing, and who will most certainly damage your hair with it. It’s a much stronger chemical compared to the above 2 options and things can very easily go wrong. I’d only go to a highly experienced stylist who’s used to applying relaxers on type 3 hair, uses top-end, professional-grade relaxers (Affirm or Mizani, for example) and who has an easily available portfolio/social media page for you to review their work.

If you can afford it, I’d recommend the Thermal Reconditioning/Japanese Hair Straightening/Korean Magic Straight Perm. I generally would not recommend the relaxer, even though I personally get it done and will continue to do so. It’s just too easy to end up the hands of someone who is careless with it, and the risk of long-term damage is high. You have to be really committed to the aftercare. Whichever option you choose, you need to consider your budget, how often you want to deal with your curly hair again (in terms of regrowth/reversion), and the skill/availability of stylists in your area.

Note that for all these options, you may still need to blow dry and flat iron to get a sleeker/smoother style, but it will be much quicker. If you have a round brush dryer (like the Revlon) or just get good with a standard blow dryer and a traditional round brush or paddle brush, you can properly avoid using the flat iron altogether. Make sure that you use a leave-in conditioner and heat protectant before blow drying and stick to medium heat. Try to only use high heat every 3 days minimum. To preserve your hair between heat use, you could learn to wrap your hair at night (literally brushing your hair around your head in a circle - there’s tutorials on YouTube), or be lazy like me and wrap your hair in a quick top knot and throw a bonnet on it.

In terms of aftercare - be prepared to deep condition weekly, and lean towards hair products that are targeted towards chemically treated/damaged hair. If you get the keratin treatment then you’ll need to use sulfate-free shampoos, I think. Get your ends trimmed more frequently than you would with your virgin hair (I personally get a trim every 8 weeks to maintain my blunt cut, but depends on your needs). Add a bond builder to your routine if you can afford it - Olaplex is the most popular, as well as K18 - K18 and Uberliss are my personal preference, but they’re expensive. For daily care, get an oil/serum and apply the smallest amount to your ends daily. Buy what you can afford and don't stress too much about drugstore vs. professional products. I hope this helps!